Management for tailings deposits: learning from experience
The tragedy at the Córrego de Feijão Mining Company (Brumadinho) in Brazil is the worst tailings catastrophe registered so far. However, even if it is no longer on the media’s front pages, it does not mean the discussion on the importance of proper management of mining tailings deposits should vanish on thin air, or that we should stop answering the questions that arise regarding our relationship with this type of structures or even the possibilities that this could happen in Chile.
The deposit in Brumadinho was inactive, just like the 469 existing deposits in Chile that do not count with specific regulatory monitoring or control requirements. How are we then safeguarding the security of our inactive deposits?
In addition, the deposit of the Córrego de Feijão Mining Company had an upstream construction design. This type of design has been forbidden in our country since 2007, a regulation that has proven to be effective, considering that of the 10 catastrophic events that have occurred in Chile since the 1960s, only one occurred after this date and was associated with the deposit’s state of abandonment. However, there are still 214 mine tailings deposits that are built upstream. Are we considering more rigorous monitoring and controls for the active ones, or evaluating the possibility of dismantling the abandoned ones given their evident high risk?
International experts recommend moving towards construction and operation methods that reduce the water content in the tailings (thickened, filtered, or paste), a relevant factor to ensure their stability. In Chile, only 16% of the total tailings deposits correspond to this design, and there does not seem to be any inclination to implement it in the newly approved projects. Should we ask ourselves about the need to promote or demand these construction methods?
In Brumadinho, the intense rainfall before the disaster apparently had an influence on the tragedy. Of the 7 faults in the last 11 years in Brazil, at least 4 were triggered by heavy rains. In Chile, the climate change effects translate into an increase in events of short duration but great intensity, and although the designs of the deposits consider the maximum probable rainfall events, they tend to change over time; so are we updating our designs? This also applies to the discussion of the probable maximum earthquake, given 9 of the 10 faults in Chile have been triggered by earthquakes.
Foto: Rogério Alves/TV Senado
The Córrego de Feijão Mining Company had a known emergency plan, but it did not work. In Chile, although there is a requirement to have specific emergency plans for mine tailings deposits, most of them have not been shared with the relevant players and no preparation of any sort for such an emergency exists. It is urgent to move forward together and generate plans that involve simulations with proven and effective warning systems.
The previous disasters at Samarco and Mount Polley brought up at an international level and also in Chile the mine tailings issue, allowing public-private initiatives to emerge such as the Programa Tranque (Tailings Dam Program), that seeks to contribute with the safe and reliable operation of tailings deposits using tools that allow monitoring key aspects related to the physical stability of the deposits and their potential impact on natural waters. This is a public-private initiative, designed and implemented by Fundación Chile along with its partners Mining Ministry, Sernageomin, ONEMI, SMA, DGA, Corporación Alta Ley, Corfo, AMSA/MLP, CODELCO, BHP, and ENAMI, and their co-executors INRIA Chile , AMTC, and Shared Value.
In September 2018, the Mining Ministry announced the guidelines of the new National Tailings Policy, which seeks to implement a sustainable management of mine tailings deposits, including, among other things, permanent monitoring and control tools with disclosed information. Although this is a significant advance, Brumadinho’s experience must generate the necessary sense of urgency to guarantee short term measures, which should translate into the consolidation of the National Tailings Observatory and the updating of national regulations. There is no such thing as a zero risk, and it is better to be transparent and prepared. Transparency, the basic principle of the National Tailings Observatory, is a strategic ally and a critical factor that promotes a new relationship with local actors, authorities, and the mining sector.